What is the difference between Type 1, 2 & 3 Cements

In the Concrete Precast industry we usually use three types of portland cement (a cement made of limestone and submarine clay), which is specified by ASTM C150. There are a total of 8 types of portland cement: I, Ia, II, IIa, III, IIIa, IV, & V. Below is a very brief synopsis of the three most popular types.

Type I: According to the NPCA this is the most commonly used cement used in most of North America. It is generally assumed unless another type is specified. It is commonly used for general construction especially when making precast and precast-prestressed concrete that is not to be in contact with soils or ground water. The typical compound compositions of this type are:

55% (C₃S), 19% (C₂S), 10% (C₃A), 7% (C₄AF), 2.8% MgO, 2.9% (SO₃), 1.0% ignition loss, and 1.0% free CaO
A limitation on the composition is that the (C₃A) shall not exceed 15%.

Type II: This type offers moderate hydration heat as well as some sulfate resistance. Type II is often used in areas with elevated sulfate levels in the soil. Because of similar price to that of Type I, Type II is much used as a general purpose cement, and the majority of Portland cement sold in North America meets this specification. Typical Composition as follows:

51% (C₃S), 24% (C₂S), 6% (C₃A), 11% (C₄AF), 2.9% MgO, 2.5% (SO₃), 0.8% ignition loss, and 1.0% free CaO

Type III: This Type can reach high strengths quickly, 1740 psi in one day. it is good when you need strength ASAP. Its typical compound composition is: 57% (C₃S), 19% (C₂S), 10% (C₃A), 7% (C₄AF), 3.0% MgO, 3.1% (SO₃), 0.9% Ignition loss, and 1.3% free CaO. Very much like Type I, but ground finer.The only downside is that the six month strength of type III is the same or slightly less than that of types I and II. Therefore the long-term strength is sacrificed a little. It is usually used for precast concrete manufacture, where high 1-day strength allows fast turnover of molds. It may also be used in emergency construction and repairs and construction of machine bases and gate installations.

For more information on Portland Cement check out:

http://en.wikipedia.org/wiki/Portland_cement#Types

https://en.wikipedia.org/wiki/Portland_cement

What happens when cement gets wet?

Why is cement such a good bonding agent for rock and sand?

When a cement particle absorbs water it grows hair (like Velcro) on the surface. This has two effects, the first is that the volume of the cement particle grows, thus filling in the open space between the rock and sand particulates. the other effect is that the "hair" that gow upon the cements hydrated surface attched and bind (like Velcro) to the other materials in the mix.

Above: Image of hydrated cement

Wet your stone

Aggregates hold water. This can be especially true with Limestone aggregates. Limestone can be very porous and can therefore absorb water. The absorbsion of stone and other aggregates can have a profound effect on mix consistentsy and product quality.

I am not sure if there is a 100% sure way to calculate you material absorbsion rate unless you are testing you materials (by saturating and weighing, then cooking out the moisture and re-weighing the materials) a couple times per day. You would also need to know the current moisture level in you materials as well, to know how much more water the will absorb. And total absorbsion is what we are concerned about.

If a mix design calls for and certain amount of stone, it is critical to know the moisture content of that stone , because water can add weight to material with out having an effect on volume. If you are meassuring you mix with a weigh belt, this could cause issues.

One issue would be that you will be likely to put a higher volume of material on the belt when it is bone dry than when the material is saturated. Another is that the dryer the material is the more moisture it will want to remove from the mix. so the dryer tit is the more you will likely add and the more water it will absorb.

If you you spray you materials to keep them at (SSD) Saturated Surface Dry, you will then be able to controls your batch consistency and product quality to a much higher degree. Saturated stone will have a consitent weight and will not try to absorb water from the mix.

Concrete Material Weights

Knowing the Specific gravity of material is important when trying to accurately pinpoint product weight. In the below chart I have given weights for the various materials that are commonly used in the production of concrete products. I have gathered these weights from various websites and texts, and believe them to be fairly accurate, but remember that material weights can very by their level of compaction. As an example, Cement can weigh any where from 50-100=lbs per cubic foot depending on it’s level of compaction.


Sand________________ 99 Lbs/Ft3
Sand (Dry)___________ 110 Lbs/Ft3
Sand (Fine)__________ 125 Lbs/Ft3
Sand (Moist)_________ 130 Lbs/Ft3
Sand (Molding)________ 78 Lbs/Ft3
Sand, Foundry________ 100 Lbs/Ft3
Sand, Foundry, Coarse___96 Lbs/Ft3
Sand, Foundry, Fine____ 104 Lbs/Ft3
Sand, Foundry, NJ Sil.___ 97 Lbs/Ft3
Silica Sand____________ 81 Lbs/Ft3
Stone Dust____________ 90 Lbs/Ft3

Expanded Shale_#4_____40 Lbs/Ft3
Expanded Shale_#8_____42 Lbs/Ft3
Pumice_______________40 Lbs/Ft3

Slate(crushed)________100 Lbs/Ft3
Granite______________97 Lbs/Ft3
Limestone____________60 Lbs/Ft3
Limestone (Ground)____59 Lbs/Ft3
Limestone(Pulv.)______ 68 Lbs/Ft3
Limestone Dust_______ 69 Lbs/Ft3

Fly Ash_____________ 65 Lbs/Ft3
Cement (Settled)______ 94 Lbs/Ft3
Cement (Fluffed)______70 Lbs/Ft3

Steel Powder_________ 150 Lbs/Ft3
Steel Grit.___________ 225 Lbs/Ft3

Concrete (compacted)___ 146 Lbs/Ft3
Concrete (mixed).______ 110 Lbs/Ft3